Solderless electrical connectors are well known in the art. See, for instance, U.S. Pats. Nos. 3,718,888, 3,511,921, and 3,936,128. One type of solderless connector is made up of a base, one or more contact members, and a cover. Base and cover consist of an insulating material, frequently a molded polymeric material such as polycarbonate, and the contact members are made of electrically conducting elastic material, e.g., phosphor bronze. Contact members typically are U-shaped, with the two upward-pointing end portions of the contact member slotted to form pairs of opposing "posts" that extend part of the length of the respective end portions of the member. Configuration of the contact members is such that, when an insulated wire is forced into the slot, the insulation is pierced and the contact member makes electrical contact with the wire conductor. The top of the connector is mated with the base to protect and insulate the splice.
Various contact member geometries are known to the prior art. For instance, in the noted U.S. Pat. No. 3,511,921, the slots used in the contact are relatively short, have parallel inner walls terminating in a bottom wall perpendicular to the parallel inner walls, whereas U.S. Pat. No. 3,718,888 discloses a contact member with tapered slots.
It is generally important that the contact member be able to accommodate a range of conductor sizes, with the wires retaining a substantial fraction of the virgin wire strength, and to be able to achieve this while exerting at least the minimum required contact force on the smallest permitted wire, and without undergoing excessive defomation upon insertion of the largest permitted wire. The above-described contact member configurations may in certain instances experience a small but still undesirable localized plastic deformation.
A slot configuration that permits the use of relatively short slots while still preventing excessive plastic deformation of the posts is disclosed in U.S. Pat. No. 3,936,128. The slots are keyhole shaped i.e., a generally parallel sided slot terminates without sharp corners in a generally rounded feature having a diameter greater than the width of the slot. Such a contact does not significantly warp or distort during wire insertion since the stresses are distributed more evenly by virtue of the keyhole slot shape. Hence, elasticity of the contact is maintained and longevity of the connection is enhanced.
For obvious reasons, it is desirable for electrical connectors, e.g, connectors for telephone wires, to be as small as possible. In particular, it is desirable that such connectors have a low profile. However, prior art slotted beam contact elements cannot be adapted to the design of a connector having very low profile. This application discloses a connector which has very low profile, yet is able to accommodate a wide range of wire sizes, and to maintain efficient reliable contact with the wire conductors, due to the fact that the contact member undergoes only a limited amount of plastic deformation during wire insertion.